Counterbore



Patented May 1, 1945 UNITED STATES PATENT OFF-ICE COUNTERBORE Joseph Lusa, Ridgefield, N. J. Application July 16, 1943, Serial No. 495,005

(CI. 17-58) I 6 Claims.

This invention relates to tools in general and especially to counterboring tools of the adjustable or exchangeable type.

One of the prime objects of the present invention is to provide .a counterboring tool wherein both the cutting bitas well as the pilot are exchangeable and are individually removable in The foregoing and still further objects and important advantages of the present invention will become more fully apparent from the ensuing description in connection with the accompanying drawing, which latter discloses one of the presently preferred forms of my device, and in which drawing:

Figure 1 is an elevation of a portion of my tool, showing the full side of the bit thereof.

Figure 2 is a similar view of my tool, with the bit in end view.

Figure 3 is a partial longitudinal section through the tool, exposing the tool bit.

Figure 4 is a bottom view of Figure 1.

Figure 5 is a similar view, with the pilot removed.

Figure 6 is a section taken on lines 6-6 of Figure 3.

Figure 7 is an enlarged perspective view of the tool bit, and

.Figure 8 is an enlarged perspective view of a pilot member.

Referring now specifically to. the figures, numeral I0 denotes the shank of my tool which is provided with an end enlargement II, forming the head of the shank. Portions of this head are removed, such as by milling and indicated at l2, in order to provide two oppositely disposed bearing faces or seats l3 for the exchangeable tool bit 14.

By the removal of the material from the head and parts of the shank body, there is provided a reduced central head portion l5, as may be readily observed from Figures 3 and 5. In that reduced central head portion is arranged a through-slot I6 of a substantially rectangular shape. The long, parallel side walls of the slot are so distanced from each other as to snugly accommodate .tool bit M. The short wall ll of the slot, remote from the end of the head, is tapered, whereas the opposite end wall [8, near the head end, is perpendicular to the longitudinal centre axis of the shank.

Tool bit M, as clearly shown in Figure '7, comprises an oblong body having a central recess IS with a straight bottom face 20. The upper or cutting ends of the bit, extending to the left and right of the recess are bevelled, as indicated at 2|, and adjacent to recess l9 there are provided spacing ridges 22, which project above the top surfaces of bit ends 2| and serve for affording chip-clearance when the tool is in operation. These projections 22 also have an additional purpose which will become evident later. Cutting ends 2! have cutting edges 23 with the required rake-clearance obtained by a simple undercutting or grinding operation, as indicated at 24.

Referring now to Figures 1 to 5, inclusive, the reduced middle portion [5 of the shank head extends into a threaded element 25 for the reception of, an exchangeable pilot 26, which latter is preferably provided with a straight end face 26 and longitudinal flutes 2'! for accommodating and gathering chips which may remain in the pilot hole from the preceding drilling operation. In Figures 1, 2 and 3 it will be seen that a wedge member 28 is placed between the tapered end wall I! of slot l6 and the straight bottom edge M of exchangeable tool bit l4. Both the wedge and the tool bit rest with their side faces against bearing or seating surfaces l3 of head enlargements 29, terminating in specially shaped end surfaces 30.

Assembly and operation In assembling my device, the tool bit H is first inserted into slot l6 so that its recess l9 engages the straight slot end l8 and thus interlocks with the, reduced center portion of the shank. In this manner the bit is centrally held in the tool shank. Now, wedge 28 is inserted between tapered end wall I! of the slot and the straight end edge of tool bit l4. I

It will be observed that bearing or seating faces 13 form extensions of the long walls of slot l6 and that the major portions of the bit side faces, opposite to its cutting edges, rest against these bearing faces I3. In this manner the tool bit is effectively supported during the boring operation.

To complete the assembly of the tool, pilot 26 of the proper size is selected and is secured to threaded element 25 of the shank. When the pilot is tightened, its straight end face 28 eventually comes to rest against projections 22, extending from tool bit l4. As will be clearly seen from Figure 2, the end face 26 of the pilot clears ends 30 of shank head enlargements 29, thus providing ample chip-clearance.

It is to be noted that the arrangement of the pilot and its relation to the tool bit is such that when the tool is in operation the pilot will have the tendency of becoming ever tighter in respect to threaded element 25, whereby the pilot: will exert a progressively increasing pressure against projections 22 of the tool bit and thereby augment the locking engagement of the tool bit by the wedge 28. Thus as the device operates, its

parts instead of chattering, as is usually induced by a strenuous machine operation, will be moresolidly united, whereby any possibility of the tool parts becoming loosened is eifectively prevented.

Attention is invited also to the arrangement of solid portions 29 of the head, and especially to a The latter are curved so their end faces 30. as to allow an unrestricted backward flow of chips between them and pilot 26. It will be also noted that the opposite seating surfaces 13 of solid head, portions 29 provide an ample support for the l'argest surface areas of bit l4, whereby the latterreceives a substantial backing during the forceful machineoperations.

It is, of course, obvious that threaded element 25,,forming the terminu of head ll, must'be trulyconcentric with the head body and with the ends of the toolbit in order to provide a true, central support for exchangeable pilot 26, which is to guide the tool bit Conclusion Thepresent invention contemplates the use, of

,a, single .tool shank, and a set of tool bits of differentsizes and a corresponding set of exchangeablepil'ot members, so that with the same tool shank any number. of counterboring operations may be performed.

While in the, foregoing description only one embodiment of the present invention is described, and only onerepresentative embodiment of my tool is illustrated in the drawing for explanatory purposes only, be; it understood that the shapejof thetool and its component parts may vary and stantially rectangular slot arranged in-the re- 1 ducedgheadportion, theshort end of the slot removedfrom. the end. ofnthethead being inclined, the headterminating in a threaded extension; agtool .bit. removably ,associated with. said slot and bearingwith itstwo opposite faces against saidvheadseats, and. having. a recess: in-engagement with the short end of the slot adjacent to said threaded extension, a. removable wedge bearing against said, bitand the inclined; short end of the slot, said. toolbit having projections adjacent to said recess andextending beyond the cutting edges of the toolbit, anda pilot removably associated with said threadedlextension and havingchip-relieving grooves and bearing with its flat bottom surface against said bit projections.

2. Ina tool of the class indicated, a shank havingan enlarged head provided with a. bit-receiving throughrslot, oppositely disposed .bit seats forming extensions of' the long walls of the slot, one of the short walls of the slot being tapered, the head terminating in a threaded extension, an exchangeable bit wedged in place between the short end Walls of the slot and having chip -relieving projections, and a pilot member removably associated with said threaded head extension and bearing against said projections.

3. In a counterbore, the combination with a tool shank having a head, the latter being provided with at least two bit seats and a reduced, slotted center portion, of a counterboring tool bit, removably placed in the head slot and having a central recess for engagement with the reduced center portion of the head, two chip -relieving spacers adjacent to the recess and extendingbeyond the cutting edges of the bit, av

threaded extension forming the terminus of the head, means for fastening the tool bit immovably in position with its cutting edges at right angles tothe longitudinal center axis of the shank, and an exchangeablepilot member having chip-relieving means secured to the threaded extension and forcibly engaging said spacers of the tool bit, while remaining substantially distanced from the head body of the tool shank.

4. In a tool of the class indicated, a tool shank having a head with oppositely disposed bit seats and a reduced central portionprovided with a slot having one of it' short walls: tapered, an exchangeable tool bit fitting intothe slot and having a central recess adapted to engage the other short wall of the slot and the adjacent part of the head central portion, with which the bit interlocks, wedge means urging the bit against said other short slot wall, a-central,threaded elementex-tendi'ngfrom theshank head, a pilot member removably engaging said element and forcibly bearing against said tool bit, so that its pressure against the tool bit increases while the tool is'being operated? 5. The combination with a slottedtool shank having an enlarged headportion and an axially extending reduced threaded end portion, the slot of the shank: being. located said enlarged head portion and having straight and tapered short end walls, of a bit having a recess at it cutting endbeing removably disposed'within the slot, the recess of the bit being adapted to engage the straight end wall ofj the slotandto straddle said reduced end portion of the shank,l-a wedge.mem.- ber driven betweenthe bit and thetapered: end wall of the slot, and an exchangeablerpilot member: in engagement with:- said. threaded: endi portionand inlforci-ble contact withsaid bit.

6.1"Ihe combination with; a one-piece slotted toolshank havingtan. enlarged head portion terminating. in, an axially extending reduced threaded endior pilot portion, the bodyofithe head; portion beingred'uced bysymmetrical;,.axe ially'progressing recesses, the slot of the; shank being disposed 1115 the: thus v,reducedhead: portion and having one straightand one; tapered short end'wall, of, an exchan eable bitplacedinthe head slot, and having. a: recess for engaging the straight end wallqoflthe slot and-for straddling said pilot portion,,wedge means; interposed between the-tapered. end wall and the bit for, bold? ing the, latter against mo,v.ement,.; and: a. pilot member removably associated with, said. threadd p lo o t o ndy nforc l n e entwi h anta, v

Ji SEPI-L Lesa 

